GDI+ Drawing in C# application

[Espen]

Hi

I have a C# application that should display a chart, the chart drawing
is done by a COM object. I have tried to use dllimport with gdi32.dll
and created compatibleDC and compatibleBitma p with the hdc from the
graphics object. The COM object is trying to draw on the compatibleDC
and I try to create a bitmap from the hdc when the c++ drawing is
finished. The image is not displaying anything, it is just black.

How is it possible to display a bitmap created from a hdc in a c#
application when the drawing is done from a C++ COM object?

Here is my sample code:

IntPtr hDC = this.CreateGrap hics().GetHdc() ;
IntPtr hMemDC = CreateCompatibl eDC(hDC); //Call gdi32.dll
IntPtr hBitmap = CreateCompatibl eBitmap(hDC);//Call gdi32.dll
SelectObject(hM emDC,hBitmap);//Call gdi32.dll
DrawChart(hMemD C);//The chart drawing done by the COM object
Bitmap bmp = System.Drawing. Image.FromHbitm ap(hBitmap);
pictureBox1.Ima ge = bmp;

Can anybody please tell me what I'm doing wrong?

Thanks!

Espen

[Dmytro Lapshyn [MVP]]

Hi,

What if you just create a System.Drawing. Bitmap class with an appropriate
pixel format, then create a Graphics instance with the static
Graphics.FromIm age method and then use the GetHdc() method on the created
Graphics instance to pass the HDC to the COM object?

--
Sincerely,
Dmytro Lapshyn [Visual Developer - Visual C# MVP]
"Espen" <es***@tiscali. no> wrote in message
news:29******** *************** ***@posting.goo gle.com...

Hi

I have a C# application that should display a chart, the chart drawing
is done by a COM object. I have tried to use dllimport with gdi32.dll
and created compatibleDC and compatibleBitma p with the hdc from the
graphics object. The COM object is trying to draw on the compatibleDC
and I try to create a bitmap from the hdc when the c++ drawing is
finished. The image is not displaying anything, it is just black.

How is it possible to display a bitmap created from a hdc in a c#
application when the drawing is done from a C++ COM object?

Here is my sample code:

IntPtr hDC = this.CreateGrap hics().GetHdc() ;
IntPtr hMemDC = CreateCompatibl eDC(hDC); //Call gdi32.dll
IntPtr hBitmap = CreateCompatibl eBitmap(hDC);//Call gdi32.dll
SelectObject(hM emDC,hBitmap);//Call gdi32.dll
DrawChart(hMemD C);//The chart drawing done by the COM object
Bitmap bmp = System.Drawing. Image.FromHbitm ap(hBitmap);
pictureBox1.Ima ge = bmp;

Can anybody please tell me what I'm doing wrong?

Thanks!

Espen

[Espen]

Hi

Thanks for the reply.

I tried your suggestion but the result was the same, the image is just
blue. My drawrect from the COM component is not showing.

Espen

es***@tiscali.n o (Espen) wrote in message news:<29******* *************** ****@posting.go ogle.com>...

Hi

I have a C# application that should display a chart, the chart drawing
is done by a COM object. I have tried to use dllimport with gdi32.dll
and created compatibleDC and compatibleBitma p with the hdc from the
graphics object. The COM object is trying to draw on the compatibleDC
and I try to create a bitmap from the hdc when the c++ drawing is
finished. The image is not displaying anything, it is just black.

How is it possible to display a bitmap created from a hdc in a c#
application when the drawing is done from a C++ COM object?

Here is my sample code:

IntPtr hDC = this.CreateGrap hics().GetHdc() ;
IntPtr hMemDC = CreateCompatibl eDC(hDC); //Call gdi32.dll
IntPtr hBitmap = CreateCompatibl eBitmap(hDC);//Call gdi32.dll
SelectObject(hM emDC,hBitmap);//Call gdi32.dll
DrawChart(hMemD C);//The chart drawing done by the COM object
Bitmap bmp = System.Drawing. Image.FromHbitm ap(hBitmap);
pictureBox1.Ima ge = bmp;

Can anybody please tell me what I'm doing wrong?

Thanks!

Espen